Field
The present invention relates to an RFID (Radio Frequency IDentification) system, and a communication device and a communication program which execute communication processing with an IC tag.
Related Art
In recent years, information management using an RFID tag is performed in various fields. A general RFID system includes an IC tag attached to an article to be a management target or an object (a pallet, a container or the like) for supporting or accommodating the article, a reader/writer to be a communication device configured to execute communication processing with the IC tag, and a host device configured to control the reader/writer.
Such an RFID system has technology for extending a communication area of the reader/writer.
Japanese Unexamined Patent Publication No. 2007-36674 discloses that an adapter coil (an extension antenna) is provided between a reader/writer and an IC tag (an RF tag).
Japanese Unexamined Patent Publication No. 2007-172419 discloses that a plurality of readers/writers (interrogators) performs a cooperative operation while performing radio communication utilizing the same frequency as a communication frequency with an IC tag.
Japanese Unexamined Patent Publication No. 2009-188498 discloses that a plurality of antennas is cascade-connected to a single reader/writer.
Japanese Unexamined Patent Publication No. 2007-79882 discloses that a plurality of readers/writers is arranged/connected so as to cause communication areas to partially overlap with each other in a daisy chain manner, and communication processing is executed during sequential transfer of a result of communication with a tag to the reader/writer connected adjacently.
Referring to the technology disclosed in the Japanese Unexamined Patent Publication Nos. 2007-36674 and 2009-188498, a communication distance is reduced even if a communication area is extended.
Referring to the technology disclosed in the Japanese Unexamined Patent Publication No. 2007-172419, moreover, there is a possibility that a radio wave to be used in communication between the readers/writers might badly influence the communication with the IC tag. In order to avoid the bad influence, it is necessary to perform complicated control. The greater the number of the readers/writers, the control is more complicated. Since the communication between the readers/writers is performed by wireless, furthermore, an installation distance between the readers/writers is limited.
Referring to the technology disclosed in the Japanese Unexamined Patent Publication No. 2007-79882, it is necessary to install the readers/writers in such a manner that parts of the communication areas overlap with each other. Therefore, a degree of freedom of an installation position is low. In addition, the radio wave is invisible. For this reason, it is impossible to confirm an overlapping state of the communication areas.